U.S. regulators on Friday approved Gilead Sciences Inc's Sovaldi, also known as sofosbuvir, as a treatment for chronic infection with the liver-destroying hepatitis C virus.
The pill is the first approved to treat certain types of hepatitis C infection without the need for interferon, an injected drug that can cause severe flu-like symptoms.
Hepatitis C, which is often undiagnosed, affects about 3.2 million Americans, killing more than 15,000 each year, mostly from illnesses such as cirrhosis and liver cancer.
Gilead said Sovaldi can be used in combination with ribavirin, an older antiviral pill, for patients with genotypes 2 and 3 infections, which account for about 28 percent of U.S. patients infected with the virus.
For patients with genotypes 1 or 4, the new drug needs to be used with both interferon and ribavirin, although it can be considered for use in patients with genotype 1 infections who cannot use interferon.
Gilead has estimated that around 70 percent of U.S. patients have genotype 1 hepatitis C infections.
The drug's approval was supported by several studies showing that it helped to eradicate the virus in significantly more patients, with fewer side effects, than the current drug regimen.
Sovaldi is the first in a new class of medications known as nucleotide analogue inhibitors, or "nukes," designed to block a specific protein that the hepatitis C virus needs to copy itself.
Analysts, on average, have forecast Sovaldi sales of $1.9 billion next year, according to BMO Capital Markets.
Shares of Gilead, which have nearly doubled over the past 12 months, were little changed in after-hours trading. The shares rose 1 percent to close at $73.99 in regular Nasdaq trading on Friday.